bug#70139: [PATCH] Improve key-translate to support removing translations

[Charalampos Mitrodimas <charmitro@posteo.net>]

This patch enhances the key-translate function to allow removing
keyboard translations by passing nil as the second argument (TO).

If TO is nil, any existing translation for the FROM key will be removed.
The compiler macro is updated to only check TO when it is non-nil.

This change makes key-translate more consistent with the behavior of
keyboard-translate, providing a way to remove translations without
having to specify the same key for both FROM and TO.

The documentation string is updated to reflect the new behavior.

* lisp/keymap.el (key-translate): support removing translations by
  passing nil as the second argument (TO). (Bug#70139)
---
 lisp/keymap.el | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/lisp/keymap.el b/lisp/keymap.el
index b2b475c7d71..1481f1fe72b 100644
--- a/lisp/keymap.el
+++ b/lisp/keymap.el
@@ -382,17 +382,19 @@ key-translate
 This function creates a `keyboard-translate-table' if necessary
 and then modifies one entry in it.
 
-Both FROM and TO should be specified by strings that satisfy `key-valid-p'."
+Both FROM and TO should be specified by strings that satisfy `key-valid-p'.
+If TO is nil, remove any existing translation for FROM."
   (declare (compiler-macro
-            (lambda (form) (keymap--compile-check from to) form)))
+            (lambda (form) (keymap--compile-check from (and to to)) form)))
   (keymap--check from)
-  (keymap--check to)
+  (when to
+    (keymap--check to))
   (or (char-table-p keyboard-translate-table)
       (setq keyboard-translate-table
             (make-char-table 'keyboard-translate-table nil)))
   (aset keyboard-translate-table
         (aref (key-parse from) 0)
-        (aref (key-parse to) 0)))
+        (and to (aref (key-parse to) 0))))
 
 (defun keymap-lookup (keymap key &optional accept-default no-remap position)
   "Return the binding for command KEY in KEYMAP.
-- 
2.34.1